The present invention relates to rotary peristaltic pumps. It concerns, more particularly, a malfunction detector particularly malfunction due to an occlusion, in a miniaturized rotary peristaltic pump intended for injecting solutions of drugs.
Miniaturized pumps for medical use have been known for several years. Light and of small dimensions, they are carried by the patient discreetly and without to discomfort, allowing him to administer, subcutaneously or intravenously, continuously or in accordance with a determined program, controlled quantities of drug solutions, without however being confined to bed and connected to a bulky, expensive and noisy machine.
Such pumps are often of the rotary peristaltic type. Their principle consists in arranging a tubing of deformable plastic material connected to a reservoir containing the drug solution and locally compressing it against a support part of rounded shape by means of rollers mounted on a rotor driven by a motor acting via a gear train. The liquid is thus sucked from the reservoir and pushed towards the outlet to be injected into the patient""s body.
FR Patent No. 2 753 235, for example, discloses a pump of this type.
When such pumps are designed, it is particularly important to concern oneself with the problem that can arise from occlusion of the tubing either because it is accidentally pinched or because the patient""s body opposes injection of the medicine. It is just as important to ensure that the rotor itself is not stopped and that it rotates properly. In both cases, it is, thus, necessary to trigger an alarm informing the patient that the injection is not occurring normally so that he immediately alerts the persons responsible.
It is an object of the present invention to provide a detector for detecting malfunction in the pump, particularly caused by an occlusion of its tubing, which is both reliable and has a low cost price.
More precisely, the invention concerns a detector for detecting malfunction in a peristaltic pump wherein a flexible tubing containing a fluid is locally compressed against a support part by means of rollers mounted on a rotor driven by a motor, this detector being characterized in that it includes:
a ring mounted so as to slide on the tubing between two extreme positions,
drive means, actuated by the rotor, for subjecting said ring to a specific reciprocating motion between said positions, and
detection means reacting to an abnormal reciprocating motion of the ring by producing an alarm signal
Preferably, the internal diameter of the ring is such that it slides freely on the flexible tubing as long as the fluid that it is conveying flows normally, but such that its movement is stopped when, because of an occlusion, the fluid no longer flows normally and causes the tubing to swell. It is then advantageous for the tubing to have locally, in the portion thereof on which the ring travels, a thinned wall such that in the event of occlusion, the swelling will occur at that location.
According to a preferred embodiment, the drive means include:
at least one stud attached to the rotor;
a drive member activated by said stud on a part of its travel and acting in turn on the ring to move it, in one direction, from its first to its second extreme position, and
a spring acting on the ring to move it, in the opposite direction, as soon as it is no longer subjected to the action of the drive member, from its second to its first extreme position.
The aforementioned drive member is, advantageously, a V-shaped spring, whose tip is fixed, one of whose branches Is activated by said stud and whose other branch acts on the ring.
Preferably, the drive means include three studs arranged at 120xc2x0 from each other on the rotor.
Advantageously, the detection means include:
a first switch closed by the ring when the latter is in its first position and open as soon as it is no longer in that position,
a second switch closed by the ring when the latter is in its second position and open as soon as it is no longer in that position, and
a circuit that has, in its memory, data representative of the moments at which said switches have to close and open when the reciprocating motion of the ring occurs according to a determined rhythm corresponding to proper operation of the pump, and whose function is to:
produce data representative of the moments at which closing and opening of the switches occurs,
compare the data contained in the memory with the data from the switches, and
produce said alarm signal when the difference between the actual switch opening and closing moments and the opening and closing moments contained in the memory exceeds a determined value corresponding to abnormal operation of the pump.
According to a preferred embodiment, said moments are those at which the ring successively:
leaves its first position,
reaches its second position,
leaves this second position, and
returns to the first position.
Preferably, said motor is a stepping motor controlled by drive pulses and said data is the number of drive pulses provided to the motor, from the moment when the ring leaves its first position, so that the latter reaches its second position, leaves this position then returns to the first position.
The ring is, advantageously, made of metal and said switches include two fixed terminals against which the ring is applied when it occupies respectively its two extreme positions, and a mobil terminal attached to the ring.